The cell conversion efficiency of crystalline silicon solar cells has reached a new high, marking the best performance in 15 years. As the most widely used technology in the solar industry, crystalline silicon has long been the standard for photovoltaic cells. The previous record of 25.0% was set by the University of New South Wales (UNSW) in 1999, but now Panasonic has broken this with an impressive 25.6% (Figure 1). This achievement not only redefines the benchmark but also highlights the ongoing progress in solar technology.
Unlike the UNSW record, which was achieved on a small 4 cm² unit, Panasonic's breakthrough was made on a larger, more practical solar cell measuring 143.7 cm². Moreover, the company developed a module using 72 of these cells, resulting in a total output of approximately 270W—25W higher than its current commercial products. This advancement shows that efficiency improvements can be scaled up for real-world applications.
Figure 1: Conversion efficiency exceeds 25%
The theoretical maximum efficiency for crystalline silicon cells is around 29%, and reaching 25–26% is considered to be near the upper limit. With Panasonic now achieving 25.6%, the industry is closely watching how much further efficiency can be improved. According to the company, their next goal is to push beyond 26%, stating, “This value should be achieved.â€
To reach this level, Panasonic introduced a new structure that combines a heterojunction design with a back contact configuration. Traditionally, heterojunction cells use an amorphous silicon layer on top of a silicon wafer to reduce carrier recombination and improve voltage. However, Panasonic’s innovation lies in removing the front-side electrodes, which are typically responsible for blocking light and reducing current flow. By shifting the contacts to the back, they increased the short-circuit current density compared to earlier versions (Figure 2).
Figure 2: Implementation with a different structure than before
While this approach boosted current, it slightly reduced the open-circuit voltage, which the company is currently investigating. One possible cause could be the increase in wafer thickness. Despite this, the overall efficiency improvement remains significant, demonstrating the potential of the back contact design.
Other companies, such as Sharp and LG Electronics, are also exploring similar technologies. Sharp, for instance, achieved 21.7% in 2012 and quickly raised it to 24.7% in 2013, then to 25.1% in April 2014. These developments suggest that research into advanced cell structures is accelerating across the industry.
Figure 3: Measurements in February 2014
Although Panasonic has not yet decided to implement this new structure in its commercial products, the company acknowledges that this method offers a new pathway to improving efficiency. They have been researching these designs for several years and are now seeing tangible results. However, integrating the back contact structure into mass production would require additional steps, such as modifying the manufacturing process or enhancing the module assembly techniques.
One challenge is the trade-off between efficiency and production complexity. While the heterojunction design allows for better stress distribution and easier thinning of wafers, the back contact structure may complicate this process. However, Panasonic believes that stress can be controlled through careful design, and they are not currently pursuing thinner wafers. For now, they are using wafers with a thickness of about 150 micrometers—similar to those used in mass production.
Looking ahead, Panasonic continues to focus on improving the efficiency of heterojunction cells. Although their current efforts are more geared toward scaling up production rather than maximizing efficiency, the recent breakthrough shows that there is still room for growth. With continued research and development, the future of solar technology looks brighter than ever.
Sacffolding Accessories
Chuzhou Jincheng Metalwork Co.,Ltd , https://www.jinchengscaffold.com